JP3104028B2 - Rubber composition for tire tread - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire tread which has excellent grip performance on dry road surfaces and wet road surfaces and exhibits good grip performance even at low temperatures such as winter.

[0002]

2. Description of the Related Art It has been generally known that, in order to improve the grip performance of a conventional rubber composition for a tire tread at a low temperature, the hardness of the tread should be lowered. And the like are mixed in the rubber composition. However, such a rubber composition using an ester plasticizer causes a decrease in hysteresis loss (tan δ), and as a result, the grip performance on a dry road surface and a wet road surface is reduced.

On the other hand, rubber compositions for tire treads which emphasize grip performance include styrene-butadiene copolymer rubber (SB) having a high styrene content as a polymer.
R) and a rubber composition filled with carbon black and a petroleum softener. But,
Such rubber compositions have relatively high glass transition points (T
g), there is a problem that the tread becomes hard at low temperatures such as in winter and grip performance deteriorates.

Attempts have been made to mix a petroleum-based softener and an ester-based plasticizer into a rubber composition at the same time as disclosed in Japanese Patent Application Laid-Open No. 60-76403 in order to suppress the decrease in grip performance at low temperatures. However, the combined use of such a petroleum softener and an ester plasticizer also causes a decrease in hysteresis loss (tan δ), and as a result, a problem that grip performance on dry road surfaces and wet road surfaces is reduced. there were.

[0005]

SUMMARY OF THE INVENTION The present invention provides a tire tread that enhances grip performance at low temperatures and maintains good grip performance under normal driving conditions (ie, grip performance on dry and wet road surfaces). It is intended to provide a rubber composition for use.

[0006]

The rubber composition for a tire tread of the present invention comprises one or two selected from the group consisting of natural rubber, polyisoprene rubber, and other diene rubbers.
To 100 parts by weight of a raw rubber mainly composed of at least one kind of rubber, a modified polyester which is a reaction product of a rosin-based natural resin, an aliphatic polybasic acid, and a polyhydric alcohol is used in an amount of 3 to 3 parts.
It is characterized by being compounded by 60 parts by weight.

As described above, in the present invention, a modified polyester which is a reaction product of a specific rosin-based natural resin, an aliphatic polybasic acid, and a polyhydric alcohol is blended and used. While maintaining good grip performance, it is possible to improve grip performance at low temperatures.

(1) Raw rubber. One or two or more rubbers selected from the group consisting of natural rubber (NR), polyisoprene rubber (IR), and other diene rubbers are used as the main components, and these rubbers are used in total.
% By weight or more. As the diene rubber, although not specified, for example, polybutadiene rubber (BR)
Styrene-butadiene copolymer rubber (SBR). These rubbers may be used alone or in a blend.

(2) Modified polyester. It is a reaction product of a rosin-based natural resin, an aliphatic polybasic acid, and a polyhydric alcohol. Rosin-based natural resins such as tall rosin, gum rosin, and wood rosin, the main components of which are abietic acid and two to five isomers thereof. Fatty acid polybasic acids It is preferred to use mainly aliphatic dibasic acids,
Tribasic acids can also be used. Higher unsaturated fatty acids having 16 to 40 carbon acids are preferably used. For example, a compound having the following formula or a mixture thereof is preferably used.

[0010]

[0011] polyhydric alcohol ethylene glycol, diethylene glycol, propylene glycol, dihydric alcohol or 1,6-hexanediol repeating units 1 to 10 of dipropylene glycol alkylene oxide polymer is preferably used. Modified polyester preferably used in the present invention,
A reaction product of the rosin-based natural resin, the aliphatic polybasic acid, and the polyhydric alcohol, for example, a compound represented by the following formula (A) or (B).

[0012]

R ₁ : a hydrocarbon residue of an aliphatic dibasic acid R ₂ : a hydrocarbon residue of a dihydric alcohol R ₃ : in the formula (A), one is a rosin residue and the other is a rosin residue or hydrogen; In the formula (B), a rosin residue R ₄ : a hydrocarbon residue of a dibasic acid other than R ₁ (for example, o, m, p-phthalic acid) (3) The rubber composition of the present invention comprises 3 to 60 parts by weight of the above modified polyester is blended with 100 parts by weight. If the amount is less than 3 parts by weight, the hardness of the rubber composition at a low temperature becomes too high, which is not preferable. On the other hand, if it exceeds 60 parts by weight, the tensile strength of the rubber composition is greatly reduced, which is not preferable.

In the rubber composition of the present invention, if necessary,
Petroleum softener, ester softener, carbon black,
Compounding agents such as zinc oxide, fatty acids, antioxidants, vulcanization accelerators, and vulcanizing agents can be arbitrarily compounded in appropriate amounts.

[0015]

EXAMPLES Raw rubber and various compounding ingredients were kneaded with a Banbury mixer according to the compounding contents (parts by weight) shown in Tables 1 and 2 to prepare a rubber composition. This rubber composition was vulcanized, and each physical property was evaluated by the following methods. The results are shown in Tables 1 and 2, respectively.

JIS hardness (0 ° C.) : JIS hardness was measured by a method of JIS K 6301 using a sample left at 0 ° C. for 1 hour. The larger this value, the worse the grip performance at low temperatures such as in winter. Hysteresis loss (tan δ) : Using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.) at a temperature of 0 ° C. and a strain rate of 10
The measurement was performed under the conditions of ± 2% and a frequency of 20 Hz. The larger this value is, the better the grip performance is.

Wet skid resistance (wet skid resistance )
Driving resistance (index) : Measured at 25 ° C. using a British portable skid tester, using a 3M safety walk as a road surface, and moistening the road surface. The greater this value, the better the grip performance on wet road surfaces.

[0018]

Note) * 1 Dioctyl sebacate * 2 Polyester having the basic structure represented by the general formula (A), where R _{3 is a} rosin-based natural resin residue, R _{2 is a} diethylene glycol residue, and R _{1 is} C _36. Dimer acid residue * 3 Polyester having a basic structure represented by the above general formula (B) where R ₄ : phthalic acid residue, R ₃ : rosin-based natural resin residue, R ₂ : diethylene glycol residue, R ₁ : C ₃₆ polyester here with the basic structure shown in dimer acid residue * 4 formula (a), R _3: rosin natural resins residue, R _2: diethylene glycol residues, R _1: C ₂₀ dicarboxylic acid residue * 5 N-oxydiethylene-2-benzothiazolesulfenamide (Noxeller MSA-G, manufactured by Ouchi Shinko Chemical Co., Ltd.)

[0020] Note) * 1, * 2, * 5 are the same as in Table 1.

In Table 1, Comparative Example 1 uses an aromatic oil used as a general petroleum softener, and Comparative Example 2 uses dioctyl sebacate used as a general ester plasticizer. It is a rubber composition used. Comparative Example 3 is a rubber composition using an aromatic oil and dioctyl sebacate together. Examples 1 to 3 are rubber compositions using the polyester represented by the general formula (A) or (B) alone.
5 is a rubber composition used in combination with an aromatic oil or dioctyl sebacate, respectively. Examples 1 to 3
This shows that the JIS hardness is relatively low while maintaining good hysteresis loss (tan δ) and wet skid resistance (index) as compared with Comparative Examples 1 and 2. In Examples 4 and 5 in which a softener was used in combination, similar effects were exhibited as compared with Comparative Examples 1 and 2 and Comparative Example 3.

Table 2 shows the results obtained by changing the raw material rubber from Table 1. In Table 2, when the same type of raw rubber is compared, that is, Example 6 is compared with Comparative Example 4, and Example 7 is compared with Comparative Examples 5 and 6, respectively.
(tanδ) and wet skid resistance (index)
This indicates that the JIS hardness was relatively low while maintaining good JIS hardness.

From these results, the rubber composition of the present invention has relatively low hardness at low temperature and relatively high hysteresis loss (tan δ) and wet skid resistance (index). It can be seen that the grip performance at low temperatures is improved and the grip performance under normal running conditions is well maintained.

[0024]

As described above, the rubber composition for a tire tread of the present invention comprises natural rubber, polyisoprene rubber,
And 1 selected from the group consisting of other diene rubbers
3 to 60 parts by weight of a modified polyester, which is a reaction product of a rosin-based natural resin, an aliphatic polybasic acid, and a polyhydric alcohol, with respect to 100 parts by weight of a raw rubber mainly composed of one or more kinds of rubber When used as a tire tread, it has a relatively low hardness at low temperatures and a relatively high hysteresis loss (tan δ) and wet skid resistance (index) due to its formulation. And the grip performance under normal running conditions can be maintained satisfactorily.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Ryokei Inoue 671-4 Mizuhashi, Noguchi-cho, Kakogawa-shi, Hyogo Inside Harima Chemicals Co., Ltd. In Harima Chemicals Co., Ltd. (72) Inventor Satoshi Iwasa 671-4 Mizuhashi, Noguchi-cho, Kakogawa City, Hyogo Prefecture In Harima Chemicals Co., Ltd. (56) References JP-A-4-39105 (JP, A) JP-A-63 JP-A-97644 (JP, A) JP-A-60-235853 (JP, A) JP-A-60-208553 (JP, A) JP-A-1-174499 (JP, A) JP-A-51-111105 (JP, A) JP-A-63-69879 (JP, A) JP-B-49-7064 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 21/00 B60C 1/00 C08L 67 / 08

Claims (3)

(57) [Claims] Claims 1. A natural rubber, a polyisoprene rubber, and 100 parts by weight of a raw rubber mainly composed of one or more rubbers selected from the group consisting of other diene rubbers.
A rubber composition for a tire tread, comprising 3 to 60 parts by weight of a modified polyester which is a reaction product of a rosin-based natural resin, an aliphatic polybasic acid, and a polyhydric alcohol. 2. The rubber composition for a tire tread according to claim 1, wherein the aliphatic polybasic acid is an aliphatic dibasic acid. 3. The rubber composition for a tire tread according to claim 1, wherein the polyhydric alcohol is a dihydric alcohol.